This invention relates to a novel flux composition for TIG welding of
stainless steel.
The invention also relates to a novel method for TIG welding.
BACKGROUND OF THE INVENTION :
TIG welding or tungsten inert gas welding uses a non-consumable
Tungsten electrode to establish the welding arc and welding can be
performed with or without filler material. An inert gas like argon or
helium is used to shield the weld metal from atmospheric contamination.
When the welding is carried out without addition of filler it is known as
autogenous TIG welding. DCEN (direct current electrode negative) is the
preferred current for welding of stainless steel.
Weld penetration is the distance that the fusion line extends below the
surface of the material being welded. Normally, welding current is of
primary importance to obtain penetration as weld penetration is directly

related to welding current. An increase or decrease in the current will
increase or decrease the weld penetration respectively.
In conventional TIG welding, there is no scope or role for flux. The
primary task of protection of weld metal from atmospheric contamination
is done by the shielding gas. TIG welding is the preferred method for
ensuring good quality of weld joint but when compared to other welding
processes suffers from low productivity i.e. deposition rate. However, in
recent years, considerable research has taken place to improve the
productivity of TIG welding. In case high penetration depth can be
achieved even with lower or normal range of welding currents, thin
sheets can be welded in one or two passes instead of the large number of
passes needed in conventional TIG welding thereby improving
productivity. Special fluxes are available called active fluxes to obtain
weld penetration in stainless steel, e.g. the flux from E O Paton electric
welding institute, Kiev, Ukraine and others but the composition is not
known.
OBJECTS OF THE INVENTION :
An object of this invention is to prepare a novel flux composition for TIG
welding of steel.
Another object of this invention is to propose a novel method for TIG
welding.
Further object of this invention is to propose a novel method for
obtaining increased penetration in TIG welding of steel.
BRIEF DESCRIPTION OF THE INVENTION;
According to this invention, there is provided a novel flux composition
comprising :
25 to 30 weight% white titanium dioxide powder,
25 to 30 weight% silicon dioxide powder, silica,
25 to 30 weight% chromium oxide green powder,
5 to 10 weight% potassium titanate powder,
5 to 10 weight% cerium oxide powder.
In accordance with this invention, there is also provided a novel method
for TIG welding comprising :
mixing the flux composition with acetone/alcohol to form a paste
appearing, the said paste on the stainless steel sheet on the top side,
drying the paste coating,
subjecting the stainless steel sheet with dried paste coating to the step of
TIG welding autogenously.
DETAILED DESCRIPTION OF THE INVENTION:
Testing was carried out with several chemicals and fluxing materials out
for their ability to increase penetration during TIG welding of
commercially pure stainless steel SS 304 5 mm thick sheets. TIG
welding was carried out using a mechanized welding setup. The speed of
welding and current are varied for a given base material thickness and
autogenous welding (no external filler was added) was carried out using
bead-on-plate trials.
Mechanised TIG welding using DCEN (direct current electrode negative)
using a drooping characteristic powder source (as in normal in TIG
welding) was used.
Flux powder was mixed with acetone/industrial alcohol and was applied
on the 5 mm stainless steel sheet on the top side. The fluxes and
acetone/industrial alcohol form a paste. The consistency of the paste
was adjusted by use of suitably adjusting quantities of acetone/alcohol
and the flu. Acetone/alcohol, being volatile liquids even at room
temperature evaporate leaving a dry coating even prior to welding. On
this dry coating, the TIG welding arc is run autogenously. A run without
any flux coating was also run to record the normal penetration in the
absence of a flux. After welding the section was cut and prepared
through metallographic methods and etched to reveal the depth of
penetration.
The dry flux had the following composition :
25 to 30 weight% : White titanium dioxide powder,
25 to 30 weight% : Silicon dioxide powder, Silica
25 to 30 weight% : Chromium oxide green powder
5 to 10 weight% : Potassium titanate dioxide powder
5 to 10 weight% : Cerium dioxide powder
After welding, cutting and metallographic preparation, it was found after
etching that the use of flux had improved penetration significantly i.e.
about 100 percent when the flux was applied as a thick layer with
suitable consistency (compared to the TIG welding without flux coating).
EXAMPLE:
Experimental Results of the invention
Base material : SS 304
Thickness : 5 mm
Sheet dimensions : 150mm X200mm X5mm (thickness)
Butt joint welded using DCEN current.
Comparison between prior art method and the inventive method in
respect of root penetration and oxidization (Give data).
Prior Art: 1.5-1.8 mm penetration needing 3-4 runs to complete the joint
Invention : 5 mm full penetration obtained
A range of the welding current used.
250 to 225 amps.
A range of the welding speed.
75-225 mm per minute

WE CLAIM :
1. A novel flux to obtain deep penetration during flux-assisted TIG
welding of stainless steel comprising :
25 to 30 weight% white titanium dioxide powder ;
25 to 30 weight% silicon dioxide powder, silica ;
25 to 30 weight% chromium oxide green powder ;
5 to 10 weight% potassium titanate powder ; and
5 to 10 weight% cerium oxide powder.
2. A method for novel TIG welding comprising :
mixing the flux composition with acetone/alcohol to form a paste
appearing, the said paste on the stainless steel sheet on the top side ;
drying the paste coating ;
subjecting the stainless steel sheet with dried paste coating to the
step of TIG welding autogenously.
3. The method as claimed in claim 2, wherein autogenous TIG
welding is carried out with DCEN (direct current electrode negative)
current without any external filler wire addition.
4. The method as claimed in claim 1, wherein due to deep
penetration of flux, the weld joint surfaces are butted together without
any need for edge preparation.

The invention provides a novel flux composition comprising 25 to 0
weight% white titanium dioxide powder, commercial grade, 25 to 30
weight% silicon dioxide powder, silica commercial grade. In accordance
with this invention, there is also provided a novel method for TIG
welding, 25 to 30 weight% chromium oxide green powder, commercial
grade, 5 to 10 weight% potassium titanate powder, commercial grade, 5
to 10 weight% cerium oxide powder, commercial grade.